Date   : Wed, 15 Oct 2008 20:40:28 +0100
From   : mike@... (Mike Tomlinson)
Subject: WD179x in an FPGA

In article <48F5DA0C.7060802@...>, Mark McDougall
<msmcdoug@...> writes

>If I recall correctly, the Beeb has a WD17xx-family controller in it.

The model B (with the disk upgrade) had an Intel 8271 by default.  There
was an Acorn upgrade to a WD1770, plus various third party DFSes, using
various controllers. I'm certain there was at least one that used the
WD1790.

The model B+ WD1770 by default.  (Actually the B+ had PCB layout for
8271 and 1770, but as far as I'm aware, it was only ever produced with
the 1770.)

The Master 128 had a 1772 by default.

> At 
>some stage in the not too distant future I'll have a go at hooking up the 
>WD179x to my Beeb implementation. Looking forward to trying out a few Beeb 
>games on it. ;)

Not sure how compatible the 179x and 177x are.  Perhaps the command set
is similar?

>I haven't even looked into the BBC emulated disk formats, but I'm assuming 
>either that there's a similar format specified, or another format which 
>contains only sector data.

The usual format is (raw) sector data, though I think you have to check
to see whether the tracks are interleaved or not on double-sided disk
images.  I've just Googled for "bbc micro disk image specification" for
you but not found anything useful.  It's been discussed here before,
perhaps a search of the archive will turn something up.

Generally, .ssd is single sided disk, .dsd is double-sided, .adf is
ADFS.  You have to examine the image to see whether it's 40 or 80 track.

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